This invention pertains to the art of knock-down shelving and, more particularly, to an improvement in the key used for locking the vertical posts and horizontal beams in assembled relationship.
The invention in particular is an improvement on the key described and illustrated in U.S. Pat. Nos. 2,760,650 and 3,490,604 and will be described with particular reference to these patents and the disclosures thereof are incorporated herein by reference. In those patents a shelving unit is described including vertical posts having a hollow rectangular cross-sectional shape with the walls having a plurality of vertically spaced, vertically extending slots. The horizontal beams are provided with plates which abut against the outer surfaces of the vertical posts and have similarly dimensioned vertically extending slots. A key is then positioned inside of the vertical post which key has hook portions projecting through aligned slots in the posts and the ends of the horizontal beams. The upper edge of each slot in the ends of the horizontal beams is then lowered so as to be within the opening of the hook portions and thus supported and locked into assembled relationship with the vertical posts.
In U.S. Pat. No. 2,760,650 the vertical height of the hook portions is slightly less than the vertical height of the vertical slots and where more than one hook portion is provided, they are spaced apart the same distance as the vertical slots. Thus, the key may be assembled with the vertical post by a simple transverse movement to have the hook portions extend through the slots. Until the horizontal beams are assembled therewith, the key is free to fall out of the slots and thus to the ground.
To overcome this problem, U.S. Pat. No. 3,490,604 proposed that the key have two hook portions with the upper hook portion having a vertical length greater than the vertical height of the slots. The horizontal beam had to be manually held in position against the posts with the vertical slots aligned. Then the key was assembled with the two by first orienting the key at an angle so that the longer hook portion would pass through the vertical slots. Then the key was rotated to bring the lower hook portion through the immediately below slot. Then the horizontal beam was lowered so as to fit in the opening part of the hook portions.
In this improvement, the key could not be assembled with the vertical post until it was in vertical position and the horizontal beam in place. This is a particularly difficult operation particularly when the horizontal beam to be installed is a substantial distance above the ground. For example, the installer had to: (1) climb the vertical post; (2) stand on the beam below; (3) hold onto the post with one hand to hold himself in position; (4) use his other hand to bring the horizontal beam into aligned relationship with the vertical post; (5) locate the key (in his pocket); (6) position the upper hook portion in the aligned slots; (7) rotate the key so that the lower hook portion goes through the next lower slot; and, (8) finally move the horizontal beam downwardly into locking relationship with the hook portions and the vertical post. Oftentimes two people are required to do this because the installer only has two hands. Because of the vertical height, there is a substantial danger of falling. Furthermore, only having two hands to simultaneously do all these operations and also hold oneself in position at the same time is quite difficult.
Furthermore, there is no way of locking permanently the horizontal beams in assembled relationship with the key and the vertical post to prevent disassembly should the horizontal beam be accidentally knocked upwardly, for example when a fork truck is loading goods onto one of the storage racks.